Vehicle telematics systems have added a powerful tool to the vehicular computing arsenal. Using a telematics control unit (TCU) and a wirelessly connected device (such as a cell phone) or on-board modem, a vehicle can access a variety of data that is stored remotely from the vehicle. At the same time, the vehicle can run off-board diagnostics, file updates, error checking and general system queries. Many off-board access requests require or request some data typically available over a vehicle CAN bus. The CAN bus connects a variety of vehicle controllers, allowing communication among controllers and further providing data resources (such as data from controllers) to remote system queries.
Implementing CAN as a main communication method on modern vehicles may necessitate taking into account bandwidth limitations of a network physical layer, multiple baud rates of the network topology and variation in subnet layouts for similar vehicle controllers implemented on different vehicle makes and models. In one example, the vehicle controllers may communicate using the same or different subnets and connection speeds. If gateways, or senders, route messages based on a predefined message type, the message type may need to be reconfigured for each vehicle configuration to ensure it reaches an intended destination. As another example, routing network messages using pre-assigned subnets may reduce flexibility in implementing a common communication system across different vehicle configurations.
Additions to a variety of implementations for the CAN bus in conjunction with the TCU, such as firmware updates and new telematics features, may exhaust the usable network 11-bit IDs. Improved transfer protocols address and work with existing limitations to allow for improved functionality and communication across a variety of subnets.